Dynamic axial compression for preparative columns using external compression

ABSTRACT

A dynamic axial compression column is disclosed herein. This dynamic axial column utilized external compression to prevent the creation of end plate space in the column. The dynamic axial column can include a tube defining a first opening, a second opening, and a lumen extending there between. The dynamic axial column can include a first end plate assembly sealing the first opening and movably extending at least partially into the lumen via the first opening, a second end plate assembly sealing the second opening, a plurality of rods extending along the outside of the tube and connecting the first end plate assembly and the second end plate assembly, and a first plurality of compression devices external to the tube and engaging one of the plurality of rods to bias the first end plate assembly towards the second end plate assembly.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present patent application claims benefit of priority to U.S.Provisional Patent Application No. 63/181,133, filed on Apr. 28, 2021,and U.S. Provisional Patent Application No. 63/161,823, filed on Mar.16, 2021, the entirety of each of which is hereby incorporated byreference for all purposes.

BACKGROUND

Chromatography is a technique for the separation of a mixture. Themixture is dissolved in a fluid (gas or liquid such as water) called themobile phase. The fluid carries the mixture through a feature thatincludes a material called the stationary phase. Different moleculeswithin the mixture remain on or in the stationary phase for differentamounts of time, causing them to separate.

The stationary phase can be media loaded and/or packed within a column.In a chromatographic separation process, the efficiency of the columnused is a key parameter. The stationary phase in a column is generally asolid product in the form of fine particles. The fine particles aretightly packed into the column to form a chromatographic bed. The columnitself is generally a hollow tube with end plates fixed at both ends tocontain the packed particles. The bottom plate is generally fixed insidethe column while the top plate can be moved up or down to allow forpacking of beds of different height.

In order to obtain a high efficiency, the arrangement of the particlesinside the column must be as homogeneous as possible. In addition, thereshould be little or no space between the underside of the top plate andthe top surface of the packed bed. For incompressible particles such assilica, hydroxyapatite, glass, etc., maintaining homogeneity andtop-plate-to-bed-surface contact can be difficult due to post-packingsettling of the chromatographic bed. Such settling can arise, forexample, during transport or while flowing the mobile phase through thecolumn. Accordingly, improvements to chromatographic columns are highlybeneficial.

BRIEF SUMMARY

One aspect of the present disclosure relates to a dynamic axialcompression column. The dynamic axial compression column includes a tubedefining a first opening, a second opening, and a lumen extending fromthe first opening through the tube to the second opening. The dynamicaxial compression column includes a first end plate assembly sealing thefirst opening and movably extending at least partially into the lumenvia the first opening, a second end plate assembly sealing the secondopening, a plurality of rods each extending along the outside of thetube and connecting the first end plate assembly and the second endplate assembly, and a first plurality of compression devices external tothe tube. In some embodiments, each of the first plurality ofcompression devices engages one of the plurality of rods and biases thefirst end plate assembly towards the second end plate assembly.

In some embodiments, the dynamic axial compression column furtherincludes media filling the lumen. In some embodiments, the media iscompressible. In some embodiments, the media is incompressible. In someembodiments, the media can be at least one of silica, alumina, zirconia,glass, hydroxyapatite, and flourapatite.

In some embodiments, the first plurality of compression devices canapply a first pressure to the media filling the lumen. In someembodiments, the first pressure is less than a maximum pressure forapplying to the media without damaging the media.

In some embodiments, the plurality of rods are at least two rods. Insome embodiments, each of the first plurality of compression devices canbe a spring. In some embodiments, the spring can be a disc spring. Insome embodiments, the disc spring can be a plurality of stacked discs.In some embodiments, at least two of the plurality of stacked discs haveopposite orientations.

In some embodiments, the dynamic axial compression column furtherincludes an equalizing plate positioned between the first plurality ofcompression devices and the first end plate assembly. In someembodiments, the equalizing plate can equally transfer force from thefirst plurality of compression devices to the first end plate assembly.

In some embodiments, the second end plate assembly movably extends atleast partially into the lumen via the second opening. In someembodiments, the dynamic axial compression column further includes asecond plurality of compression devices. In some embodiments, each ofthe second plurality of compression devices are external to the tube. Insome embodiments, each of the second plurality of compression devicesengage one of the plurality of rods and bias the second end plateassembly towards the first end plate assembly.

In some embodiments, the first plurality of compression devices canapply a first pressure to bias the first end plate assembly towards thesecond end plate assembly. In some embodiments, the first pressure isequal to or greater than a backpressure in the chromatography column andthereby eliminates headspace creation.

In some embodiments, the tube is circular. In some embodiments, the tubehas a diameter of at least three centimeters. In some embodiments, thefirst end plate assembly includes a first inward face. In someembodiments, the second end plate assembly includes a second inwardface. In some embodiments, each of the first inward face and the secondinward face are covered by a frit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a portion of a chromatography column.

FIG. 2 is a perspective view of another portion of a chromatographycolumn.

FIG. 3 is one embodiment of a dynamic axial compression column.

FIG. 4 is a perspective view of one embodiment of a disc of a discspring.

FIG. 5 is a side view of one embodiment of a stack of discs forming adisc spring.

FIG. 6 is a view of an embodiment of a chromatography column includingan equalizing plate.

FIG. 7 is a view of another embodiment of the chromatography column.

FIG. 8 is a schematic depiction of the movement of the first end plateof a chromatography column with respect to the second end plate of thechromatography column.

DETAILED DESCRIPTION

Efficiency and/or effectiveness of a chromatography column at leastpartially depends on the homogeneity of the packing of thechromatographic bed. Specifically, the formation of voids or channelswithin the chromatographic bed decreases the efficiency andeffectiveness of the column.

High efficiency requires that the particles inside the packed bed of thecolumn must be as homogeneous and stable as possible. However,maintaining such homogeneity and stability can be difficult due tosettling of the chromatographic bed after packing that can arise due tomovement or jostling of the column such as can occur during transport,storage, or installation, or due to the flowing of the mobile phasethrough the column. Additional settling can result in a void at the topof the column which decreases bed efficiency.

FIGS. 1 and 2 are views of portions of chromatography columns 100 and200. Cavities 101 and 201 have formed in the packed beds 101 and 102,respectively, and there are liquid-filled spaces between the packed bedsand the end plate assemblies of the columns. In these figures the columnwas operated with flow entering at the bottom of the column and exitingat the top. The continued settling of the resin after packing thuspermitted the entire bed to be pushed upwards during flow, creatingvoids at the bottom of the column bed. Had flow been in a downwardsdirection, the voids would have formed at the top of the column bed.

The presence of cavities 101 and 201, and the end spaces in columns 100and 200 can result in the non-uniform movement of mobile phase throughthe columns 100 and 200. Portions of the mobile phase passing throughthe cavities and end spaces travel the vertical distance faster thanportions of the mobile phase passing through the chromatography bed viaa longer path. Those skilled in the art recognize that this differentialflow of the mobile phase can create multiple and/or non-ideal peaks,leading to decreased column performance.

Embodiments of the present disclosure relate to dynamic axialcompression columns that can eliminate and/or minimize the formation ofcavities and end spaces within the bed of the column irrespective of thedirection of flow

Specifically, the dynamic axial compression columns comprise a tubedefining a lumen. This tube has a first (top) end assembly and a second(bottom) end assembly, which when inserted into the tube bound the lumenand define a lumen space within the tube extending between a firstopening in the first (top) end and a second opening in the second(bottom) end. The first (top) end assembly can be movable with respectto the second (bottom) end assembly, and with respect to the tube suchthat a distance between the first (top) end assembly and the second(bottom) end assembly can change. In some embodiments, pressure on thefirst (top) end plate can cause movement of the first (top) end assemblytowards the second (bottom) end assembly that decreases the distancebetween the first (top) end assembly and the second (bottom) endassembly. This decrease in distance can decrease a volume of the lumenspace.

In this document, “first” and “top”, when referencing an end assembly orpart thereof, are used interchangeably. The words “second” and “bottom”are similarly used interchangeably. The terms are descriptive only anddo not necessarily refer to the relative heights above the ground of theend assembly or part thereof during use. That is, if the column isinverted, what is described in this document as “top” would to anobserver be seen as the “bottom” and vice versa.

In some embodiments, the first end assembly can be biased towards thesecond end assembly by a compression device. Due to this biasing, thefirst and the second end assemblies can move closer together in theevent of any settling of the media in the column, thereby preventing theformation of a cavity. This compression device is external to the lumen.

With reference to FIG. 3 , one embodiment of the column 300 is shown,which column 300 can be a chromatography column 300, also referred toherein as a dynamic axial compression column 300. The column 300includes tube 302, having a first end 346 and a second end 348, anddefining a lumen 304. The tube 302 can comprise a variety of shapes andsizes and can be made from a variety of materials. In some embodiments,the tube 302 can be circular. The tube 302 can be made from any desiredmaterials, including one or several metals, alloys, polymers,composites, glass, or the like. In some embodiments, a material can beselected to handle a desired range of pressures and mobile phasesthrough the tube 302.

As seen in FIG. 3 , the column 300 can comprise a first end assembly306, also referred to herein as a first end plate assembly 306, a topend assembly 306, or a top end plate assembly 306, and a second endassembly 308, also referred to herein a second end plate assembly 308, abottom end assembly 308, or a bottom end plate assembly 308. In someembodiments, each end assembly 306, 308 can be comprised of an end plate310 which is external to tube 302; an insert 312; and optionally a frit320 which can be in contact with the lower surface of insert 312. Theend assembly 306, 308 also contains a sealing mechanism 314 such as anO-ring, gasket, inflatable bladder and the like, which prevents materialfrom within the lumen from escaping the tube during operation of thecolumn.

In some embodiments, the end plate 310 and insert 312 are a singlepiece. In some embodiments, the end plate 310 and insert 312 are twodistinct pieces joined together

Each of the first and second end assemblies can comprise a variety ofshapes and sizes and can be made from a variety of materials. In someembodiments, one or more of the component parts of the end assembliescan be made from one or several metals, alloys, polymers, composites,combinations of the foregoing or the like. In some embodiments, amaterial can be selected to handle a desired range of pressures andmobile phases through the tube 302.

With reference to FIG. 3 , in the case of the lower end assembly, in oneembodiment the end plate can be in direct contact with the lower end oftube 302. In the case of the upper assembly, in one embodiment a gap 318can optionally exist between the bottom surface of the end plate 310 andthe top surface of tube 302.

In some embodiments, the top end assembly can move with respect to thetube 302 while the sealing mechanism 314 can continue to seal the topopening 350, also referred to herein as a first opening 350, of the tube302. The top opening 350 can be located in the first end 346 of the tube302. In some embodiments, for example, the top end assembly can movewith respect to the tube 302 such that distance 318 decreases anddistance 316 increases. Specifically, in some embodiments, as the mediawithin the lumen settles or further compresses, movement of the top endassembly 306 towards the bottom end assembly 308 will cause the volumeof the lumen space to decrease and eliminate any cavities or end spaceswhich may form.

In some embodiments, the bottom end assembly 308, via similar featuresto the top end assembly 306, can be movable with respect to the top endassembly 306 and/or with respect to the tube 302. In some embodiments,the bottom end assembly 308 can be fixed with respect to the tube 302.The bottom end assembly 308 can, in some embodiments, seal a bottomopening 352, also referred to herein as a second opening 352, of thetube 302. The bottom opening 352 can be located in the second end 348 ofthe tube 302.

Each of the first and second heads 306, 308 can include an inward face313. Thus, the first head 306 can have a first inward face 313 and thesecond head 308 can have a second inward face 313. In some embodiments,the inward face 313 of the heads 306, 308 is the portion of the insertthat extends furthest into the lumen 304 of the elongate member 302. Insome embodiments, and as shown in FIG. 3 , each of the inward faces 306,308 is covered by a frit 320. The frit 320 can comprise a porous memberthat allows the passing of mobile phase while preventing the passing ofthe stationary phase. The frit 320 can comprise, for example, a mesh, ascreen, fritted glass, fritted plastic, sintered ceramic or metal, orthe like.

The top and bottom end assemblies 306, 308 can be coupled and/orconnected via a plurality of rods 322. The rods 322 can comprise avariety of shapes and sizes and can be made from a variety of materials.In some embodiments, each of the rods 322, as depicted in FIG. 3 , canextend along the outside of the tube 302 and can connect the top endassembly 306 and the bottom end assembly 308, and specifically canconnect the end plate 310 of the top end assembly 306 to the end plate310 of the bottom end assembly 308. In some embodiments, each of therods 322 extends through a hole in the end plate 310 of the first headassembly 306 to allow the top end plate assembly 306 to move withrespect to the rods 322. In some embodiments, each of the rods 322extends through a hole in the end plate 310 bottom end assembly 308 toallow the bottom end plate 310 to move with respect to the rods 322.

In some embodiments, the plurality of rods 322 can comprise any desirednumber of rods 322. In some embodiments, the plurality of rods 322 cancomprise, for example, at least two rods 322, at least three rods 322,at least four rods 322, or the like. In some embodiments, the number ofrods can increase as the width or diameter of the tube 302 increases.

Each of the rods 322 can include a first end 324 and a second end 326.In some embodiments each of the first and second ends 324, 326 cancomprise a stop feature 328. The stop feature 328 can be configured toengage with one of the end plate assemblies 306, 308, and specificallywith one of the end plates 310 of the end plate assemblies 306, 308 toprevent movement of the end plate assembly 306, 308, and specificallythe end plate 310 beyond that stop feature 328. In some embodiments, thestop features 328 can comprise a nut, a flange, a snap ring, a cotterpin, or the like. In some embodiments in which, for example, the bottomend assembly 308 is not movable with respect to the rod 322, the stopfeature 328 can comprise physical connection between the rod 322 and thebottom end assembly 308, and specifically the end plate 310 of thebottom end assembly such as, for example, a weld. In some embodiments,the stop feature 328 can comprise a nut, and each of the first andsecond ends 324, 326 of the rods 322 can be threaded so as to screw intoand thereby engage the nut.

In some embodiments, and as depicted in FIG. 3 , the chromatographycolumn 300 can comprise a plurality of compression devices 330. Each ofthese compression devices can be external to the tube 302, and each ofthese compression devices 330 can engage with one of the rods 322 andone of the end plate assemblies 306, 308 to thereby move the endassemblies 306, 308 towards each other. In the embodiment depicted inFIG. 3 , each of the rods 322 has a compression device 330 which engageswith the rod 322, and specifically engages with the rod 322 via therod's 322 stop feature 328 and with the top end plate assembly 306 andspecifically with the base 310 of the top end plate assembly 306. Thecompression devices 330 can generate and apply a first force to othercomponents of the chromatography column 300 to bias the first end plateassembly 306 towards the second end plate assembly 308.

Each of the compression devices 330 can comprise a member configured togenerate a biasing force. In some embodiments, each of the compressiondevices 330 can comprise a spring such as, for example, a coil spring, adisc spring, a wave-spring, or the like. In some embodiments in whichthe spring comprises a disc spring, the disc spring can comprise aplurality of discs 400 as shown in FIG. 4 , which discs 400 can bearranged to form a stack 500 as shown in FIG. 5 . In some embodiments,one or several of the compression devices 330 can comprise a pneumaticcylinder, a hydraulic cylinder, a polymer compression device, a metallicspring, a polymer spring, or the like. Thus, in some embodiments, eachof the compression devices 330 can comprise a plurality of stacked discs400. In some embodiments, the stack 500 can comprise a parallel stack inwhich all of the discs 400 in the stack 500 have the same orientation,or a series stack or a parallel-series stack in which some of the discs400, or in other words in which at least two of the discs 400 in thestack 500 have opposite orientations.

In some embodiments in which the first end plate assembly 306 moves withrespect to the tube 302, the compression devices 330 can comprise afirst set of compression devices 330. As shown in embodiment shown inFIG. 7 , a view of another embodiment of the chromatography column 700,also referred to herein as column 700 or as dynamic axial compressioncolumn, each of the first end plate assembly 306 and the second endplate assembly 308 move with respect to the tube 302, and thecompression devices 330 can comprise a first set of compression devices330-A, also referred to herein as a first plurality of compressiondevices 330-A, and a second set of compression devices 330-B, alsoreferred to herein as a second plurality of compression devices 330-B.In some embodiments, the first set of compression devices 330-A canengage with the rods 322 and the first end plate assembly 306 and thesecond set of compression devices 330-B can engage with the rods 322 andthe second end plate assembly 308. In some embodiments, each of thefirst and second sets of compression devices 330-A, 330-B can beexternal to the lumen 304 and the tube 302, each of the first set ofcompression devices 330-A can engage one of the rods 322 and bias thefirst end plate assembly 306 towards the second end plate assembly 308,and each of the second set of compression devices 330-B can engage oneof the rods 322 and bias the second end plate assembly 308 towards thefirst end plate assembly 306. In some embodiments, this can include thefirst set of compression devices 330-A applying a first force and/orpressure to bias the first end plate assembly 306 towards the second endplate assembly 308. In some embodiments, and as shown in FIG. 6 , thefluid flowing within the chromatography column 700 can exert a pressureagainst all surfaces of the column 700. This pressure, referred to as abackpressure, is indicated by arrows 380 in FIG. 6 . If the backpressureexceed the pressure generated by the compression devices 330, then aheadspace can be created in the chromatography column 700.

In some embodiments, the first pressure applied by the first set ofcompression devices 330-A is equal to or greater than the backpressurein the chromatography column 700 to eliminate headspace creation. Insome embodiments, the first pressure is less than a maximum pressure forapplying to the media without destroying, damaging, or fracturing themedia.

In some embodiments, the plurality of compression devices 330 aretogether configured to apply a force and/or a pressure to bias the firstend plate assembly 306 towards the second end plate assembly 308. Insome embodiments, the plurality of compression devices 330 are togetherconfigured to apply a force and/or a pressure to the media containedwithin the lumen 304.

In some embodiments in which the stop feature 328 comprises a nut, thestop feature 328 can be adjusted to change a compression of thecompression devices 330. In some embodiments, this changing of thecompression of the compression devices 330 can change the force appliedby the compression devices 330 to bias the first end plate assembly 306towards the second end plate assembly 308. In some embodiments,adjusting the stop feature 328 can include, for example, tightening orloosening the nut comprising the stop feature 328. In some embodiments,for example, the nut comprising the stop feature 328 can be tightened orloosened until a desired torque of the nut is reached.

With reference now to FIG. 6 , a view of another embodiment of thechromatography column 600, also referred to herein as column 600 or asdynamic axial compression column is shown. The column 600 can includethe components and features of column 300 shown in FIG. 3 . However, thecolumn 600 shown in FIG. 6 can include one or more equalizing plates602. The equalizing plate 602 can comprise an intermediate memberlocated between the compression devices 330 and one of the end plateassemblies 306, 308. In some embodiments in which each of the end plateassemblies 306, 308 is moveable with to the tube 302, and as shown inFIG. 7 , a first equalizing plate 602-A can be located between firstcompression devices 330-A and the first end plate assembly 306, and asecond equalizing plate 602-B can be located between second compressiondevices 330-B and the second end plate assembly 308.

In the embodiment of FIG. 6 , the equalizing plate 602 is locatedbetween the compression devices 330 and the first end plate assembly306. The equalizing plate 602 can comprise a variety of shapes and sizesand can be made from a variety of materials.

The equalizing plate 602 can be configured to receive force from thecompression devices 330 and apply this force equally across the surfaceof the end plate(s) 310 contacted by the equalizing plate 602, and thusequally across the end plate assembly 306, 308 contacted by theequalizing plate 602. Thus, in the embodiment shown in FIG. 6 , theequalizing plate 602 equally transfers force from the compressiondevices 330 to the first end plate assembly 306.

In some embodiments, this equal application of force to the end plate310 results in the end plate assembly 306, 308 applying equal force tothe media in the lumen 304. Further, in the event that the end plateassembly 306, 308 moves with respect to the tube 302, the equalapplication of force to the end plate 310 results in the end plateassembly 306, 308, and specifically the insert 312, equally moving withrespect to the tube 302 such that the inward faces of the first andsecond inserts 312 and frits 320 (those faces in contact with the lumen)are and remain parallel.

With reference now to FIG. 8 , a schematic depiction of the movement ofthe first end plate assembly 306 with respect to the second end plateassembly 308 and the tube 302 in a series of chromatography columns 800,also referred to herein as columns 800 or as dynamic axial compressioncolumns 800 is shown. FIG. 8 depicts a single column 800 having a firstend plate assembly 306 in three different positions. The column 800includes the tube 302 defining a lumen 304. The lumen 304 is filled withmedia 802. The media can be compressible or incompressible. In someembodiments, the media 802 can be an incompressible media comprising atleast one of: silica; alumina; zirconia; glass; hydroxyapatite; andflourapatite. In some embodiment, the media 802 can comprise a solidproduct in the form of fine particles that are packed into the lumen 304for a chromatographic bed.

The column 800 includes the first and second end plate assemblies 306,308 as described above. The first end plate assembly 306 is biasedtowards the second end plate assembly 308 by compression devices 330.The compression devices 330 apply a pressure to the media 802 fillingthe lumen 304 by applying a force to first end plate assembly 306. Thispressure applied to the media can be less than a maximum pressure forapplying to the media 802 without destroying, damaging, or fracturingthe media 802.

As seen in FIG. 8 , the first end plate assembly 306 of column 800-A isin a first position, the first end plate assembly 306 of column 800-B isin a second position, and the first end plate assembly 306 of column800-C is in a third position. In some embodiments, each of the columns800 can include the same amount of media 802, but the media in columns800-B, 800-C has settled and/or compressed more than the media 802 incolumn 800-A. As the media 802 settles, the compression devices 330apply a force to the first end plate assembly 306 such that the firstend plate assembly 306 advances from the first position to the secondposition, and then upon further compression and/or settling, to thethird position. Due to this advance of the first end plate assembly 306into the lumen, cavities and/or end plate space are prevented fromforming. Thus, this movement of the first end plate assembly 306 cancorrespond to the compaction of the chromatographic bed.

This description should not be interpreted as implying any particularorder or arrangement among or between various steps or elements exceptwhen the order of individual steps or arrangement of elements isexplicitly described. Different arrangements of the components depictedin the drawings or described above, as well as components and steps notshown or described are possible. Similarly, some features andsub-combinations are useful and may be employed without reference toother features and sub-combinations. Embodiments of the invention havebeen described for illustrative and not restrictive purposes, andalternative embodiments will become apparent to readers of this patent.Accordingly, the present invention is not limited to the embodimentsdescribed above or depicted in the drawings, and various embodiments andmodifications may be made without departing from the scope of the claimsbelow.

What is claimed is:
 1. A dynamic axial compression column comprising: atube defining: a first opening, a second opening, and a lumen extendingfrom the first opening through the tube to the second opening; a firstend plate assembly sealing the first opening and movably extending atleast partially into the lumen via the first opening; a second end plateassembly sealing the second opening; a plurality of rods each extendingalong an outside of the tube and connecting the first end plate assemblyand the second end plate assembly; and a first plurality of compressiondevices external to the tube, each of the first plurality of compressiondevices engaging one of the plurality of rods and biasing the first endplate assembly towards the second end plate assembly, wherein each ofthe first plurality of compression devices comprises a spring.
 2. Thedynamic axial compression column of claim 1, further comprising mediafilling the lumen.
 3. The dynamic axial compression column of claim 2,wherein the media is compressible.
 4. The dynamic axial compressioncolumn of claim 2, wherein the media is incompressible.
 5. The dynamicaxial compression column of claim 4, wherein the media comprises atleast one of: silica; alumina; zirconia; glass; hydroxyapatite; andflourapatite.
 6. The dynamic axial compression column of claim 4,wherein the first plurality of compression devices are configured toapply a first pressure to the media filling the lumen.
 7. The dynamicaxial compression column of claim 6, wherein the first pressure is lessthan a maximum pressure for applying to the media without damaging themedia.
 8. The dynamic axial compression column of claim 1, wherein theplurality of rods comprise at least two rods.
 9. The dynamic axialcompression column of claim 1, wherein the spring comprises a discspring.
 10. The dynamic axial compression column of claim 9, wherein thedisc spring comprises a plurality of stacked discs.
 11. The dynamicaxial compression column of claim 10, wherein at least two of theplurality of stacked discs have opposite orientations.
 12. The dynamicaxial compression column of claim 1, wherein the second end plateassembly movably extends at least partially into the lumen via thesecond opening.
 13. The dynamic axial compression column of claim 1,wherein the first plurality of compression devices are configured toapply a first pressure to bias the first end plate assembly towards thesecond end plate assembly.
 14. The dynamic axial compression column ofclaim 13, wherein the first pressure is equal to or greater than abackpressure in the column and thereby eliminates headspace creation.15. The dynamic axial compression column of claim 1, wherein the tube iscircular.
 16. The dynamic axial compression column of claim 15, whereinthe tube has a diameter of at least three centimeters.
 17. The dynamicaxial compression column of claim 1, wherein the first end plateassembly comprises a first inward face, and wherein the second end plateassembly comprises a second inward face, and wherein each of the firstinward face and the second inward face are covered by a frit.
 18. Adynamic axial compression column comprising: a tube defining: a firstopening, a second opening, and a lumen extending from the first openingthrough the tube to the second opening; a first end plate assemblysealing the first opening and movably extending at least partially intothe lumen via the first opening; a second end plate assembly sealing thesecond opening; a plurality of rods each extending along an outside ofthe tube and connecting the first end plate assembly and the second endplate assembly; a first plurality of compression devices external to thetube, each of the first plurality of compression devices engaging one ofthe plurality of rods and biasing the first end plate assembly towardsthe second end plate assembly; and an equalizing plate positionedbetween the first plurality of compression devices and the first endplate assembly, the equalizing plate configured to equally transferforce from the first plurality of compression devices to the first endplate assembly.
 19. A dynamic axial compression column comprising: atube defining: a first opening, a second opening, and a lumen extendingfrom the first opening through the tube to the second opening; a firstend plate assembly sealing the first opening and movably extending atleast partially into the lumen via the first opening; a second end plateassembly sealing the second opening; a plurality of rods each extendingalong an outside of the tube and connecting the first end plate assemblyand the second end plate assembly; a first plurality of compressiondevices external to the tube, each of the first plurality of compressiondevices engaging one of the plurality of rods and biasing the first endplate assembly towards the second end plate assembly; and a secondplurality of compression devices.
 20. The dynamic axial compressioncolumn of claim 19, wherein each of the second plurality of compressiondevices are external to the tube, and wherein each of the secondplurality of compression devices engage one of the plurality of rods andbias the second end plate assembly towards the first end plate assembly.21. The dynamic axial compression column of claim 20, further comprisinga second equalizing plate positioned between the second plurality ofcompression devices and the second end plate assembly, the secondequalizing plate configured to equally transfer force from the secondplurality of compression devices to the second end plate assembly.